Used with
permission of Maiken Naylor, University at Buffalo, Buffalo, NY, USA,
http://ublib.buffalo.edu/libraries/units/sel/exhibits/stamps
Blaise Pascal (1623-62), the French philosopher remembered by many college students of that language for his Pensees, was also a mathematician and physicist of note. He defended Toricelli's assertion that a vacuum existed in the enclosed end of a barometer, and that air had weight. He took a barometer up a mountain, demonstrating that air became thinner with altitude and therefore exerted less pressure to counterbalance a column of mercury. Pascal worked out the hydraulic principle, that pressure is transferred through a fluid in an enclosed container, and he also developed a calculating machine that was capable of adding and subtracting. Like for many other inventors of calculating devices, technical difficulties encountered here outweighed sound principles.